1. Technical Field
The present invention relates to sonar imaging, and in particular sidescan sonar and forward looking sonar imaging.
2. Related Art
Sidescan Sonar (SSS) is used for surveying large areas of the sea floor for sea bottom targets. Side-scan sonar uses a device that emits sonar pulses down toward the seafloor across a narrow angle perpendicular to the path of the sensor through the water. Reflections from the seafloor are recorded in across-track slices. When stitched together along the direction of motion, these slices form an amplitude image of the seafloor within the beam coverage.
Forward Looking Sonar (FLS) is used to provide a real time view of the seafloor in front of the vehicle. The sonar pulse is emitted in a narrow beam that is scanned across a field of view about the direction of travel to form radial slices of the sea floor. When stitched together, perpendicular to the direction of motion, these slices form an amplitude image of the sea floor.
SSS and FLS images are often searched visually by an operator to identify objects on the seafloor. This is time consuming and subject to human error. Automatic Target Recognition (ATR) algorithms can assist operators to identify sea bottom targets. Properly applied, this reduces the time taken to analyse a large survey and increases confidence in the results.
Whilst ATR algorithms help detect targets, the performance of current generation ATR algorithms is often specific to sensor payload and operational conditions. Particularly with supervised filter response algorithms, a small change to the speed of the vehicle or the Time Variable Gain (TVG) can cause a large drop in the probability of detection.